Atlasaurus

MEANING: Lusotanian giant

PERIOD: Middle Jurassic

CONTINENT: Africa

Atlasaurus is a brachiosaurid sauropod dinosaur from the Middle Jurassic period of what is now Morocco. A basal member of the brachiosauridae, Atlasaurus had the longer forelimbs typical of this group, but a proportionately larger head, shorter neck, and longer tail. Atlasaurus is estimated at around 15 m in length, and weighed about 23 t.

Atlasaurus is from the Middle Jurassic. The Middle Jurassic, spanning from approximately 174 to 163 million years ago, was a period of increasing tectonic activity and evolutionary innovation. By this time, the supercontinent Pangaea had begun to split more significantly, with Laurasia in the north and Gondwana in the south drifting apart. This movement created new coastlines, shallow seas, and rift valleys that fostered diverse ecosystems. The climate remained generally warm and humid, promoting the spread of lush vegetation, including ferns, cycads, and conifers, which blanketed much of the land and supported a wide variety of herbivorous dinosaurs.

Though less well known than the Late Jurassic, the Middle Jurassic was an important evolutionary chapter. Several major dinosaur groups began to diversify, including the stegosaurs and more derived long-necked sauropods that would later dominate the landscape. Theropods also continued to evolve, giving rise to new lineages like the megalosaurids and the early ancestors of more derived carnivores. Fossil evidence from this interval is relatively scarce compared to later stages, but what we do have paints a picture of an increasingly complex world, setting the stage for the iconic ecosystems of the Late Jurassic.

Atlasaurus is a brachiosaurid. Brachiosauridae is a distinctive family of sauropod dinosaurs best known for their unusual limb proportions and towering stance. Unlike most other sauropods, brachiosaurids had longer front legs than hind legs, giving their bodies an upward tilt and allowing them to reach higher vegetation than their contemporaries. Their long necks, elevated shoulders, and deep chests contributed to a giraffe-like silhouette, and this anatomical design likely allowed them to browse tall conifer forests with minimal competition.

Brachiosaurids first appeared in the Middle Jurassic and persisted into the Early Cretaceous. Fossils have been found across North and South America, Europe, Asia, and Africa. These dinosaurs were massive, the tallest potentially exceeding 12 meters in height. While not as long as some of the later titanosaurs, brachiosaurids were among the most impressive of the Jurassic giants. Their high-browsing niche and colossal size made them a key component of their ecosystems, shaping the structure of ancient forests and the evolution of other herbivores and predators alike.